I do think we will see a lot of Thor's rogue gallery, but most cameos. Especially since it was said a few days ago that the movie will be filled with Thor mythos. Karnilla appearing may be a possibility, but anyone outside of Malekith, and Kurse, POSSIBLY hela, would most likely be brief scenes, or cameos.

Which I think would be great. Cause even if he doesn't have anything to do with them, it lets us know that they DO exist in the MCU

yeah, i still want at least a cameo for Hela. And of course, Karnilla was very nearly in Thor 1, according to an audio interview with the writers from a while back, they actually had a big thing going on with Nornheim in the early drafts, and it was on the list of things Marvel wanted (Karnilla and Nornheim). And of course, the deleted scene mentions a battle at Nornheim, though that's not canon and they could certainly rework some of what they were originally going to do there in Thor 1 to fit Thor 2.

I know Krige mentioned it being a small part and she might be unrecognizable, but I don't think that necessarily means CGI or a lot of makeup to look like a crone or whatever. If they stick a big wild black wig on her, and make her up to look like a wicked sorceress/Queen, with amazing costume, and crazy headdress, well... that may very well be what she means by that comment.

Now of course, Karnilla could be in it, and it's not Krige, but I'm just using her because she's the one who we don't know the character for, and whenever they don't say who someone is playing, it immediately points to being someone significant that the fans will get really excited about (and I dont consider Alfyse or even some Ragnarok prophesizing old crone significant enough to hold that information back ). Also, consider that if they go with an older Karnilla (just as they appear to have gone with an older Tyr as well) then they can just allude to her being in love with some perfect guy in the past and it never worked out, and she's bitter over that, and so bypass any mention of Balder who doesn't appear to be getting used in the MCU at all. (which I think is a good thing as I think he would bloat even more an already huge cast, and wouldn't be done justice as a character in that case)